The present invention relates to apparatus for the separation of a product from quantities of much smaller particles mixed with the product. (Such devices are often referred to in the trade as "elutriators".)
The removal of fines (e.g., dust) from a granular or pellet-like product is a long-standing problem in many industries. Naturally, there have been many proposals for dealing with this problem including washing and settling systems. Vertical air-assisted (e.g., vacuum) separators have also been proposed (e.g., Forsberg, U.S. Pat. No. 2,950,006; Mackenzie et al., U.S. Pat. No. 3,833,117; Mackenzie et al., U.S. Pat. No. 3,904,515; and Thomson U.S. Pat. No. 3,448,856).
The general type of system, as well as the particular constructional details, most suitable for such a separating or cleaning operation can depend upon the physical characteristics of both the product and the impurities. A particular separation problem has grown along with the growth of the modern plastics industry. In many plastic molding and extruding operations the input product to the forming machinery consists of pellets or granules of the particular material involved (e.g., polyethylene).